The purposes of this study are to test a combination of two anticancer drugs, O6Benzylguanine and BCNU, and determine if the degree of anticancer activity can be improved over that of BCNU alone and to determine an effective dose of O6BG and the dose of BCNU that can be administered safely with O6BG. Preliminary findings indicate a poor correlation between O6-alkylguanine DNA alkyltransferase activity in peripheral blood monomuclear cells and tumor tissue.